Soldering flux for aluminium.



OARLETON ELLIS AND OW J.

SOLDERlitlG FLUX 'Patented December 15, 1903.

Pn rnnr OFFICE.

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SiPEClFIGATION forming part of Letters Patent No. 746,802, dated December 15, 1903.

Application filed December 31,1902.

To all whom, it may concern:

Be it known that We, CARLETON ELLIS and OWEN J. FLANIGAN, both of Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful improvements in Soldering Fluxes for Aluminium, of which the following is a specification.

Up to the present time great difficulty been experienced in the soldering of aluminium owing to the highly repellent action which this metal exhibits toward solders of all hin ds. This difficulty is due partly to a film of alumina which coats the surface of the metal and partly to a characteristic property of aluminium-viz. its disinclination to alloy with other metals.

The object of our inven ion is to overcome the above difficulties by the use of a flux which not only dissolves and removes the coating of alumina, but which also gives to the aluminium an attractive rather than a repellant action toward solders.

The principle involved. in our invention is that of using for a flux the heavy metal salts whose heat of formation is less than that of the corresponding salt of the metal to be soldered, combined with a vehicle possessing reducing properties. Such metallic salts when heated in the presence of the vehicle and in contact with the metal to be soldered are reduced by the vehicle and the metal to be soldered to the metallic state, and th us coat or thermoplate the metal. On this coated metal the solder flows readily and unites easily to form a perfect metallic contact. in practice the operation of thermoplating is made simultaneously with that of soldering, the liurt and solder being applied to the metal at the same time.

Among the metallic salts reacting as here-- tofore described are the chloride of mercury and silver. Silver chlorid, for instance, incorporated with the reducing vehicle when heated on a sheet of aluminium gives rise to aluminium chlorid, which volatilizes, and the reduced silver liberated in the nascent state unites With the aluminium, iorming an aluminium-silver alloy, over which the solder readily fiows. On cooling, the solder will be found to be firmly attached to the aluminium plate. So perfect is the adhesion that two;

Serial No.13'7,224=. (N0 specimens.)

strips of aluminium soldered together in this manner cannot be torn apart at the soldered junction. The aluminium itself will yield first. The other halide salts of silver and those of gold, mercury, and bismuth actin a similar manner. Further,itisnotnecessarythatthe metallic salt employed has a heat of reaction less than that of the metal to be soldered if there be present other bodies which by metathesis or otherwise are capable of forming salts having the requisite thermochemical properties. For instance, an equivalent for chlorid of mercury could be a mixture of mercuric acetate sodium chlorid; an equivalentfor fluorid of bismuth could be a mixture of hismuth nitrate and ammonium fiuorid or naphthylamin hydrofluorid. These combinations tending to produce equivalents as heretofore stated are in general unsatisfactory and imperfect in action. It is therefore preferable to use directly the salts having the thermochemical properties as heretofore specified. In Cuba?! to facilitate this thermoplating action, the metallic salt is incorporated with an rganic body, which acts as a reducing vehicle. This vehicle may consist of an oil stock, as paraflin-oil or Vaseline, in which case the flux takes the form of apaste, or the salt may be incorporated with a molten wax or resin and cast into sticks or pencils. The use of a reducing vehicle for applying the metallic salt is an important feature of this invention. Were the salt of itself without a medium of any sort to be used, its reduction would occur wholly at the expense of the aluminium, causing the latter to b come etched and corroded. The vehicle materially aids the thermoplating action by partly or completely reducing the salt to the metallic state, liberating the metal in the nascent form.

What we claim, and desire to secure by Letters Patent, is

1. Theherein-described flux forsoldering metals consisting of a salt of a metal whose heat of formation is less than that of the cor responding salt of the metal to be soldered combined with a reducing vehicle, substantially as described.

2. The herein-described flux for soldering aluminium consisting of asalt of ametal whose responding salt of aluminium combined with a reducing vehicle, substantially as described.

3. The herein-described flux for soldering aluminium consisting" of the-chlorids of the heavy metals combined with an organic reducing vehicle, substantially as described.

at. The herein-described flux for soldering aluminium consisting of the chlorids of silver combined With an organic reducing vehicle, I substantially as described.

heat of formation is less than that of the cor- I 

